A number of curing agents for epoxy resins are known in the art, as well as a variety of methods for preparing epoxy curing compositions. Related, copending U.S. patent application Ser. No. 07/078,308 contains an extensive survey of art in this area. The invention described in that application concerns novel polyamidopolyamines. The products are prepared by the sequential reaction of an aliphatic or aromatic di-primary amine with a reaction product of at least a molar excess of an aromatic or aliphatic dicarboxylic acid with a polyoxyethylene, a polyoxypropylene or a poly(oxyethylene/oxypropylene)diamine or triamine. The reaction takes place at a temperature of about 150.degree.-250.degree. C.
The references found fail to disclose any urea-linked trifunctional aromatic amine terminated compositions. Urea linkages are desirable because they are more stable and, in general, add more toughness to a polymer.
The present invention, using low temperatures produces a triamine derivative composition which is terminated with aromatic amines and contains urea linkages. Further, formation of the product does not require a catalyst when high molecular weight triamines are the reactants. It was observed that in the case of low molecular weight triamines there were problems with gelation. However, in an alternate embodiment trifunctional polyether triols were used instead of triamines and reacted at fairly mild temperatures in the presence of a tin catalyst to form trifunctional aromatic amines in two steps while avoiding problems with gelation.
These compositions are useful for applications such as epoxy coatings. The products are especially adapted for use in Reaction Injection Molding because their reactivity with isocyanates is very suitable. Other uses may be apparent to those skilled in the art.